\documentclass{standalone}
\usepackage{tikz}
\usepackage{ctex,siunitx}
\setCJKmainfont{Noto Serif CJK SC}
\usepackage{tkz-euclide}
\usepackage{amsmath}
\usepackage{wasysym}
\usepackage{circuitikz}
\usetikzlibrary{patterns, calc}
\usetikzlibrary {decorations.pathmorphing, decorations.pathreplacing, decorations.shapes}
\ctikzset{bipoles/length=1cm}
\begin{document}
\small
\begin{circuitikz}[>=latex, scale=0.6,european]
  % \useasboundingbox(0.9,0)rectangle(5.1,5);
  \draw (0,0) to [R=$2$, *-*] (5,0) to [R=$1$, *-*] (2.5, 4) to [R=$3$] (0,0);
  \draw (5,0)--(5,-2)--(-4,-2)node[left]{$B$};
  \draw (0,0)--(-4,0)node[left]{$C$};
  \draw (2.5,4)--(-4,4)node[left]{$A$};
  \foreach \x in {0,-2,4}
  {
      \draw [fill=white] (-4,\x) circle (3pt);
  }
  \draw [<->] (-3.5,0)--node[fill=white]{$U_{\text{线}}$}(-3.5,4);
  \draw [->](-2,4)--(-1,4) node [above]{$I_{\text{线}}$};
  \draw [->](2.5, 4)--(2,4-.8)node [left]{$I_{\text{相}}$};
  \draw [->](2.5, 4)--(3,4-.8)node [right]{$I_{\text{相}}$};
\end{circuitikz}
\end{document}